> This is old hat for PCs, but to release a new, faster model that is perfectly backwards compatible is almost unprecedented in the console world.

Nintendo has done this for years with their consoles. You can play Game Boy games on the Game Boy Color and Game Boy Advance (1989 -> 2001), Gamecube games on the Wii and Wii games on the Wii U. The same was true for Playstation 2 games in the first few versions of the Playstation 3.

There will definitely be games that require a Playstation Neo and will not run on the Playstation 4.